Here are some with an explanation on why each would be a good addition to the forum.

1) http://www.wunderground.com/maps/ This map shows current placements of where cold fronts/low pressures are at. Useful when you want to know how much longer you have until a cold front is through, or where exactly that all important low pressure is located.

2) http://www.livewxradar.com/ There are two radars here. They both stream live (whereas our current radar just is a still frame, those two are able to show the precip in the past to tell you where the precip may just be going)

These are just two I found. If someone can find any better maps that show the same things as these two do, then I'm all for it.

A very useful page put up and maintained by the NWS that shows how much rainfall/snowfall there could be up to 5 days away, potential hazards highlighted, probability maps that show how good of a chance there is of recieving x amount of snow/rain in a given day, surface analysis, and more.